1. Lesson Overview
1.3 Studying Life

2. THINK ABOUT IT
Think about important news stories you’ve heard. Bird flu spreads around the world, killing birds and threatening a human epidemic. Users of certain illegal drugs experience permanent damage to their brains and nervous systems. Reports surface about efforts to clone human cells.
These and many other stories involve biology—the science that employs scientific methodology to study living things. The Greek word bios means “life,” and -logy means “study of.”

3. Characteristics of Living Things
Biology is the study of life. But what is life?
No single characteristic is enough to describe a living thing. Also, some nonliving things share one or more traits with organisms.
Some things, such as viruses, exist at the border between organisms and nonliving things.

4. Characteristics of Living Things
What characteristics do all living things share?
Living things are
made up of basic units called cells,
are based on a universal genetic code,
obtain and use materials and energy,
grow and develop,
reproduce,
respond to their environment,
maintain a stable internal environment,
and change over time.

5. Characteristics of Living Things
Living things are made up of one or more cells—the smallest units considered fully alive.
Living things consist of only a single cell and are called unicellular organisms.
Cells in multicellular organisms display many different sizes, shapes, and functions.
Cells can grow, respond to their surroundings, and reproduce. Despite their small size, cells are complex and highly organized.

6. Characteristics of Living Things
Living things are based on a universal genetic code.
All organisms store the complex information they need to live, grow, and reproduce in a genetic code written in a molecule called DNA.
That information is copied and passed from parent to offspring and is almost identical in every organism on Earth.

7. Characteristics of Living Things
Living things grow and develop.
During development, a single fertilized egg divides again and again.
As these cells divide, they differentiate, which means they begin to look different from one another and to perform different functions.

8. Characteristics of Living Things
Living things respond to their environment.
A stimulus is a signal to which an organism responds.
For example, some plants can produce unsavory chemicals to ward off caterpillars that feed on their leaves.

9. Characteristics of Living Things
Living things reproduce, which means that they produce new similar organisms.
Most plants and animals engage in sexual reproduction, in which cells from two parents unite to form the first cell of a new organism.

10. Characteristics of Living Things
Other organisms reproduce through asexual reproduction, in which a single organism produces offspring identical to itself.
A yeast cell budding into two is an example of asexual reproduction.

11. Characteristics of Living Things
Living things maintain a relatively stable internal environment, even when external conditions change dramatically.
All living organisms expend energy to keep conditions inside their cells within certain limits. This condition process is called homeostasis.
For example, specialized cells help leaves regulate gases that enter and leave the plant.

12. Characteristics of Living Things
Living things obtain and use material and energy to grow, develop, and reproduce.
The combination of chemical reactions through which an organism builds up or breaks down materials is called metabolism.
For example, leaves obtain energy from the sun and gases from the air. These materials then take part in various metabolic reactions within the leaves.

13. Characteristics of Living Things
Over generations, populations of organisms evolve, or change over time.
Insects become resistant to pesticides and bacteria become resistant to antibiotics.

14. Big Ideas in Biology
What are the central themes of biology?

15. Big Ideas in Biology
What are the central themes of biology?
The study of biology revolves around several interlocking big ideas: The cellular basis of life; information and heredity; matter and energy; growth, development, and reproduction; homeostasis; evolution; structure and function; unity and diversity of life; interdependence in nature; and science as a way of knowing.

16. Big Ideas in Biology
All biological sciences are tied together by “big ideas” that overlap and interlock with one another.
Several of these big ideas overlap with the characteristics of life or the nature of science.

17. Information and Heredity
Living things are based on a universal genetic code.
The information coded in your DNA is similar to organisms that lived 3.5 billion years ago.
The DNA inside your cells right now can influence your future—your risk of getting cancer, the amount of cholesterol in your blood, and the color of your children’s hair.

18. Matter and Energy
Life requires matter that serves as nutrients to build body structures, and energy that fuels life’s processes.
Some organisms, such as plants, obtain energy from sunlight and take up nutrients from air, water, and soil.
Other organisms, including most animals, eat plants or other animals to obtain both nutrients and energy.
The need for matter and energy link all living things on Earth in a web of interdependent relationships.

19. Growth, Development, and Reproduction
All living things reproduce. Newly produced individuals grow and develop as they mature.
During growth and development, generalized cells typically become more different and specialized for particular functions.
Specialized cells build tissues, such as brains, muscles, and digestive organs, that serve various functions.

20. Homeostasis
Living things maintain a relatively stable internal environment.
For most organisms, any breakdown of homeostasis may have serious or even fatal consequences.
Specialized plant cells help leaves regulate gases that enter and leave the plant.

21. Evolution
Groups of living things evolve. Evolutionary change links all forms of life to a common origin more than 3.5 billion years ago.

22. Evolution
Evidence of this shared history is found in all aspects of living and fossil organisms, from physical features to structures of proteins to sequences of information in DNA.
Evolutionary theory is the central organizing principle of all biological and biomedical sciences.

23. Structure and Function
Each major group of organisms has evolved its own collection of structures that have evolved in ways that make particular functions possible.
Organisms use structures that have evolved into different forms as species have adapted to life in different environments.

24. Unity and Diversity of Life
Life takes a variety of forms. Yet, all living things are fundamentally similar at the molecular level.
All organisms are composed of a common set of carbon-based molecules, store information in a common genetic code, and use proteins to build their structures and carry out their functions.
Evolutionary theory explains both this unity of life and its diversity.

25. Interdependence in Nature
All forms of life on Earth are connected into a biosphere, or “living planet.”
Within the biosphere, organisms are linked to one another and to the land, water, and air around them.
Relationships between organisms and their environments depend on the cycling of matter and the flow of energy.

26. Science as a Way of Knowing
The job of science is to use observations, questions, and experiments to explain the natural world in terms of natural forces and events.
To make certain that scientific knowledge is used for the benefit of society, all of us must understand the nature of science.

27. Fields of Biology
How do different fields of biology differ in their approach to studying life?
Biology includes many overlapping fields that use different tools to study life from the level of molecules to the entire planet.

28. Global Ecology
Global ecological studies are enabling us to learn about our global impact, which affects all life on Earth.
For example, an ecologist may monitor lichens in a forest in efforts to study the effects of air pollution on forest health.

29. Biotechnology
The field of biotechnology is based on our ability to “edit” and rewrite the genetic code. We may soon learn to correct or replace damaged genes that cause inherited diseases or genetically engineer bacteria to clean up toxic wastes.
Biotechnology raises enormous ethical, legal, and social questions.

30. Building the Tree of Life
Biologists have discovered and identified roughly 1.8 million different kinds of living organisms, and researchers estimate that somewhere between 2 and 100 million more forms of life are waiting to be discovered around the globe. This paleontologist studies signs of ancient life—fossilized dinosaur dung!

31. Building the Tree of Life
In addition to identifying and cataloguing all these life forms, biologists aim to combine the latest genetic information with computer technology to organize all living things into a single universal “Tree of All Life”—and put the results on the Web in a form that anyone can access.

32. Ecology and Evolution of Infectious Diseases
The relationships between hosts and pathogens are dynamic and constantly changing.
Organisms that cause human disease have their own ecology, which involves our bodies, medicines we take, and our interactions with each other and the environment. Understanding these interactions is crucial to safeguarding our future.

33. Ecology and Evolution of Infectious Diseases
For example, a wildlife biologist studies a group of wild gelada baboons. Pathogens in wild animal populations may evolve to infect humans.

34. Genomics and Molecular Biology
These fields focus on studies of DNA and other molecules inside cells. Genomics is now looking at the entire sets of DNA code contained in a wide range of organisms.
Computer analyses enable researchers to compare vast databases of genetic information in search of keys to the mysteries of growth, development, aging, cancer, and the history of life on Earth.

35. Scientific Measurement
So data is uniform throughout the world, scientists use the metric system when collecting data and performing experiments.
The metric system is a decimal system of measurement whose units are based on certain physical standards and are scaled on multiples of 10.

36. Scientific Measurement: Common Metric Units